Error when select product

Step to reproduce:

+ Go to Pages app, add a product detail component on page.

+ Choose a product which the price is null as below image:

Problem: 

Development Notes:
Stream/optional APIs are not well handling for retrieve product information. Potential NPE or 

NoSuchElementException (call optional.get() without check, or accessing properties without null check) can be thrown.

see CommercetoolsProduct#populatePrice -> call get() without check
CommercetoolsProduct#populateImageURLs -> productProjection.getMasterVariant().getImages()

We need to check and do some refactor to ensure that the APIs are using correctly.